Interoprabilty between devices is one of the hallmarks of modern electronic devices. There are many instances where two devices need to work in conjunction with each other to accomplish a particular task. For instance, if a portable electronic device is to be charged, an appropriate power supply is needed that can connect with the electronic device and provide the requisite power to charge the electronic device.
Also, often it may be useful to ensure that the two or more devices are connected together before exchanging signals. This may be needed to ensure safety and/or security for the devices involved.